Dicopper(I) oxalate complexes for use as precursor substances in metallic copper deposition

ABSTRACT

The invention relates to dicopper(I) oxalate complexes stabilised by neutral Lewis base components and to the use thereof as precursors for the deposition of metallic copper. The neutral Lewis bases used are alkynes or alkenes containing at least one silyl or ester group, or nitrites, saturated or unsaturated nitrogen ligands, phosphites, trialkyl-phosphines or oxygen- or sulfur-containing ligands.

The invention relates to dicopper(I) oxalate complexes stabilised byneutral Lewis base components and to the use thereof as precursors forthe deposition of metallic copper. The neutral Lewis bases used arealkynes or alkenes containing at least one silyl or ester group, ornitriles, saturated or unsaturated nitrogen ligands, phosphites,trialkyl-phosphines or oxygen- or sulfur-containing ligands.

1. PRIOR ART AND OBJECT OF THE INVENTION

For the deposition of thin copper films on substrates, manyorgano-copper precursors have now been disclosed. Copper compounds inthe oxidation state +1 containing a β-diketonate ligand and a neutralLewis base L, such as, for example, an alkene or alkyne, have proven tobe highly promising substances. Complexes of this type and the usethereof as precursors in the CVD (chemical vapour deposition) processare described, for example, in U.S. Pat. No. 5,220,044, WO 00/71550, WO00/17278, U.S. Pat. No. 6,130,345 or Chem. Mater. 2001, 13, 3993; Inorg.Chem. 2001, 40, 6167; Chem. Mater. 1992, 4, 365; Organometallics 2001,20, 4001. Preference is given to the use of fluorine-containingβ-diketonate ligands, such as, for example, hexafluoroacetylacetonate,since the corresponding copper(I) complexes have much higher thermalstability and higher volatility than their fluorine-free analogues.Fluorine-free copper(I) β-diketonate complexes, such as, for example,alkyne-stabilised copper(I) acetylacetonates, are extremelyoxygen-sensitive, decompose even at 0° C. (Chem. Ber. 1995, 128, 525)and are thus no longer suitable as precursors for the CVD process. Thedeposition of the copper layer takes place in a thermally induceddisproportionation in accordance with the following equation:2 LCu^(I)(β-diketonate)→Cu⁰+Cu^(II)(β-diketonate)₂+2 L

The resultant Cu^(II)(β-diketonate)₂ and Lewis base L are volatile underthe conditions used in the CVD process and can thus be removed from thesystem. Ideally, a highly pure copper film remains. However, only 50% ofthe copper(I) precursor employed can be converted into copper(0) in thisreaction, the remaining 50% ending in the correspondingCu^(II)(β-diketonate)₂. The same result is obtained on use of β-ketoesters instead of β-diketones, as described, for example, in WO 00/08225or U.S. Pat. No. 5,441,766. However, it has proven disadvantageous onuse of fluorine-containing copper(I) precursors that the adhesion of thecopper films to various substrate surfaces is not perfect, which canprobably be attributed to the van der Waals forces of the fluorine atomsin the precursor molecule and thus to repulsive interactions. Inaddition, there is a risk of contamination of the wafer inmicroelectronics, especially of the silicon with fluorine, which resultsin the wafer being unusable.

Complete conversion to copper is achieved using Lewis base-stabilisedcopper(I) alkoxides of the formula LCu^(I)OR (EP 0468396) and Lewisbase-stabilised cyclopentadienylcopper(I) compounds of the formulaLCu^(I)(η⁵-C₅R₅), described in EP 0297348 and DE 4124686. Some of theexamples in the said patents are even fluorine-free and stable at 25° C.However, since the thermal decomposition reactions do not proceed in adefined manner in these cases, free-radical species are formed in thedecomposition reactions, unfortunately resulting in contaminated copperfilms (oxygen about 5%, carbon about 1%) (MRS Bulletin/August 1994, 41;Chem. Mater. 1992, 4, 577).

The object of the present invention was therefore to providefluorine-free copper(I) precursors for the deposition of metallic copperwhich are simple and inexpensive to prepare, are stable thermally and ifpossible to air and can be converted completely into metallic copperfilms by thermal methods in a defined decomposition reaction in thetemperature range from about 50 to 400° C. with formation of definedmolecular, copper-free, nontoxic and if possible gaseous by-products.Further objects of the present invention are, in addition to a processfor the preparation of the precursor substances according to theinvention which can be carried out simply and inexpensively, also toprovide a suitable process for the preparation of thin, highly purecopper films or layers with the aid of these precursors and thus alsoimproved highly pure, thin copper layers.

The object is achieved by compounds of the general formula (I)

in which copper is in the oxidation state +1, and

-   L is R—C≡C—R′ having at least one silyl or ester group, R′HC═CHR    having at least one silyl or ester group, R′₃Si—C≡C—R′, R′₃N,    R′₂N(CH₂)_(n)NR′₂, substituted or unsubstituted 2,2′-bipyridine,    1,10-phenanthroline, P(OR′)₃, P(alkyl)₃, R′—O—R′, R′—O(CH₂)_(n)O—R′,    R′—S—R′, R′—S(CH₂)_(n)S—R′ or a nitrile from the group consisting of    CH₃—C≡N, ^(t)Bu—C≡N, C₄H₉C≡N and Ph—C≡N,    where-   R is A, aryl, alkylaryl or alkynyl having at least one SiR′₃ or    COOR′ group, and-   R′ is R, H, A, aryl, alkylaryl or alkynyl,    where L, R and R′ may each, independently of one another, adopt    identical or different meanings in different positions of the    molecule,-   A is straight-chain or branched C1–C30-alkyl, C3–C30-cycloalkyl,    straight-chain or branched C2–C30-alkenyl or straight-chain or    branched C3–C30-cycloalkenyl,-   aryl is C6–C10-aryl or alkylaryl,-   alkylaryl is C7–C18-alkylaryl,-   alkynyl is straight-chain or branched C2–C30-alkynyl.

Compounds according to the invention are therefore also compounds of thegeneral formula (I) in which

-   A is straight-chain or branched C1–C9-alkyl, straight-chain or    branched C3–C9-cycloalkyl, straight-chain or branched C2–C9-alkenyl    or straight-chain or branched C3–C9-cyclo-alkenyl,-   aryl is phenyl or naphthyl,-   alkylaryl is tolyl or mesityl,-   alkynyl is straight-chain or branched C2–C9-alkynyl,    and L, R and R′ may each, independently of one another, adopt    identical or different meanings in different positions of the    molecule.

Sub-groups are formed by compounds of the general formula (I) in which

I.

-   A is straight-chain or branched C1–C4-alkyl from the group    consisting of methyl, ethyl, n- and i-propyl and n-, i- and    tert-butyl, C3–C6-cycloalkyl from the group consisting of    cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl, straight-chain    or branched C2–C6-alkenyl from the group consisting of vinyl,    propenyl, butenyl, pentenyl and hexenyl, or C3–C6-cycloalkenyl from    the group consisting of cyclopropenyl, cyclobutenyl, cyclopentenyl,    cyclopenta-dienyl and methylcyclopentadienyl,-   aryl is phenyl or naphthyl,-   alkylaryl is tolyl or mesityl,-   alkynyl is straight-chain or branched C2–C6-alkynyl from the group    consisting of ethynyl, propynyl, butynyl, pentynyl and hexynyl,    and R and R′ may each, independently of one another, adopt identical    or different meanings in different positions of the molecule,    or    II.-   L is R—C≡C—R′ or R′HC═CHR, each having at least one silyl or ester    group, and the radicals R and R′ are as defined in claim 1,    or    III.-   L is R′₃Si—C≡C—R′,    where-   R′ is SiMe₃, CH₃, C₂H₅, C₃H₇, C₄H₉, phenyl, COOMe or COOEt,    or    IV.-   L is an alkyne selected from the group consisting of    Me₃Si—C≡C—SiMe₃, Me₃Si—C≡C—^(n)Bu, MeOOC—C≡C—COOMe, EtOOC—C≡C—COOEt    and Me₃Si—C≡C—R′, in which R′ is CH₃, C₂H₅, C₃H₇, phenyl, COOMe or    COOEt,    or    V.-   L is an alkene selected from the group consisting of H₂C═CHSiMe₃,    H₂C═CHCOOCH₃, H₂C═CHCOOC₂H₅ and H₂C═CHSiR′₃, in which R′,    independently of one another, is CH₃, C₂H₅, C₃H₇, C₄H₉, HC═CH₂ or    phenyl,    or    VI.-   L is a compound selected from the group consisting of CH₃—C≡N,    ^(t)Bu C≡N, C₄H₉C≡N, Ph—C≡N; N(CH₃)₃, N(C₂H₅)₃, H₂N—(CH₂)₂—NH₂,    (CH₃)₂N—(CH₂)₂—N(CH₃)₂, (C₂H₅)₂N—(CH₂)₂—N(C₂H₅)₂, H₂N—(CH₂)₄—NH₂,    (CH₃)₂N—(CH₂)₄—N(CH₃)₂, (C₂H₅)₂N—(CH₂)₄—N(C₂H₅)₂,    2,9-dimethyl-1,10phenanthroline; P(OCH₃)₃, P(OC₂H₅)₃, P(OC₆H₁₁)₃,    P(OPh)₃; P(CH₃)₃, P(C₂H₅)₃, P(C₃H₇)₃, P(C₄H₉)₃, P(C₆H₁₁)₃;    C₂H₅—O—C₂H₅, CH₃—O—C₄H₉, CH₃O—(CH₂)₂—OCH₃, C₂H₅O—(CH₂)₂—OC₂H₅,    CH₃—S—CH₃, C₂H₅—S—C₂H₅, C₃H₇—S—C₃H₇, Ph—S—Ph, CH₃S—(CH₂)₂—SCH₃,    CH₃S—(CH₂)₃—SCH₃, C₂H₅S—(CH₂)₂—SC₂H₅ and PhS—(CH₂)₂—SPh.

In particular, the object of the present invention is achieved by thenovel compounds of the general formula (I):

-   -   di{[bis(trimethylsilyl)acetylene]copper(I)}oxalate,    -   di{[(trimethylsilyl)(n-butyl)acetylene]copper(I)}oxalate,    -   di[(vinyl-t-butyldimethylsilyl)copper(I)]oxalate and    -   di[(vinyldiethylmethylsilane)copper(I)]oxalate.

The object of the present invention is also achieved by a process forthe preparation of the compounds of the general formula (I) as indicatedby reacting Cu₂O with oxalic acid and a Lewis base L in an inertsolvent, and isolating the resultant product. In particular, the objectis achieved by the particular embodiments of the process as claimed inclaims 11 to 21.

In accordance with the invention, the compounds of the general formula(I) according to claims 1 to 9 are used for the production of highlypure, thin metallic copper layers.

Highly pure, thin metallic copper layers are produced by a process inwhich compounds of the general formula (I) are heated, causingelimination of the Lewis base L and deposition of metallic copperthrough decarboxylation.

The elimination of the Lewis base L is carried out at a temperature inthe range from about 50 to about 200° C. The decarboxylation withformation of metallic copper and carbon dioxide which takes place as thesecond reaction is completed at a temperature in the range from about150 to 350° C.

The Lewis base L eliminated is recycled and re-employed in a process forthe preparation of the compounds of the general formula (I) and used forthe production of highly pure, thin metallic copper layers.

The object according to the invention is thus achieved, in particular,by highly pure, thin metallic copper layers having improved propertiesproduced using a compound of the general formula (I) in the processaccording to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the decomposition of thedi{[bis(trimethylsilyl)acetylene]-copper(I)}oxalate prepared as afunction of temperature with deposition of a thin copper layer on asubstrate.

FIG. 2 shows the decomposition of thedi{[(trimethylsilyl)(n-butyl)-acetylene]copper(I)}oxalate prepared as afunction of temperature with deposition of a thin copper layer on asubstrate.

FIG. 3 shows the decomposition of thedi[(vinyl-t-butyldimethylsilane)-copper(I)]oxalate prepared as afunction of temperature with deposition of a thin copper layer on asubstrate.

FIG. 4 shows the decomposition of thedi[(vinyldiethylmethylsilane)-copper(I)]oxalate prepared as a functionof temperature with deposition of a thin copper layer on a substrate.

2. DESCRIPTION OF THE INVENTION

The present invention provides compounds of the general formula (I)

in each of which, independently of the position in the complex and ofone another,

L is an alkyne R—C≡C—R′ or alkene R′HC═CHR which contains at least onesilyl or ester group. L may furthermore be a nitrile R′—C≡N, a saturatedor unsaturated nitrogen ligand, a phosphite P(OR′)₃, a trialkylphosphineP(alkyl)₃, an ether R′—O—R′, a diether, a thioether R′—S—R′ or adithioether. The oxidation state of the copper is +1.

R can be alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, alkylaryl oralkynyl having at least one SiR′₃ or COOR′ group.

R′ can, independently of one another, be R or H, alkyl, cycloalkyl,alkenyl, cycloalkenyl, aryl, alkylaryl or alkynyl.

The compounds of the general formula (I) are prepared by reaction ofCu₂O, oxalic acid and the neutral ligand L or the two different neutralligands in an inert aprotic organic solvent. The compounds of thegeneral formula (I) can be isolated in the pure form astemperature-stable substances. In addition, the substances obtained aredistinguished by surprisingly and unusually high oxidation stability;they can be handled in air without problems, which enormously simplifiessubsequent use of the substances as precursors for the deposition ofmetallic copper.

If the compounds of the general formula (I) are heated, a highly purecopper mirror remains; all by-products are volatile and can thus beremoved from the reaction site very simply. The thermal decompositionproceeds in accordance with the following equation:

The only reaction products formed, besides metallic copper, are carbondioxide and the Lewis base L, which can be regenerated and re-used.

The compounds of the general formula (I) can be used as precursors forthe deposition of metallic copper. The deposition can be carried outfrom the gas phase or from a solution of precursor and a suitablesolvent or from the solid state of the precursor through contact of theprecursor with a heated substrate. It is advantageous compared with theprior art that copper(I) precursors with which metallic copper can bedeposited to the extent of 100% in a defined free-radical-freedecomposition reaction with formation of highly pure copper films areaccessible for the first time. The yield of deposited metallic coppercan thus be increased from 50 to 100% compared with the prior art. Thehigh stability and insensitivity of the compounds, in particular thehigh oxidation stability, enormously simplify handling of the compoundsin the process for the deposition of metallic copper and thus have afavourable effect on the deposition process in terms of cost.

The advantages of the compounds of the general formula (I) compared withthe substance used in the prior art (CupraSelect®) are thus: betterphysical properties, such as higher thermal stability, better chemicalproperties, such as higher oxidation stability, simpler handling, lessexpensive synthesis owing to the much cheaper starting material oxalicacid compared with hexafluoroacetylacetone, double the yield of metalliccopper in the deposition process, copper-free and nontoxic by-products,fewer by-products and thus less environmental pollution. In addition,the compounds contain no fluorine atoms which can result in fluorinecontamination and thus in the wafers being unusable.

Overall, the synthesis of the copper(I) precursors according to theinvention is thus simpler and less expensive than that of thecommercially available copper(I) precursor CupraSelect®, which is(trimethyl-vinylsilane)copper(I) hexafluoroacetylacetonate. At the sametime, the precursors according to the invention enable both the qualityof the copper coatings to be increased and the environmentalfriendliness of the process to be increased.

3. DETAILED DESCRIPTION OF THE INVENTION

Compounds of the general formula (I) according to the invention containan oxalate dianion and two copper centres in the oxidation state +1,where the oxalate dianion is bonded as a bridge in a μ-1,2,3,4 mode tothe two copper(I) centres. The dicopper(I) oxalate unit CuO₂C₂O₂Cu isstabilised by coordination of neutral ligands L to one copper(I) centreeach, preferably two identical ligands L, so that the two copper(I)centres have an at least pseudo-trigonal-planar, if desired also atetrahedral environment. The copper atoms present in the complex may bebonded to two different ligands L. For simplification, reference isgenerally made below to the ligand or Lewis base L, although this mayalso be taken to mean two different ligands or Lewis bases L.

L is an alkyne R—C≡C—R′ or alkene R′HC═CHR which contains at least onesilyl or ester group. L may furthermore be a nitrile R′—C≡N, a saturatedor unsaturated nitrogen ligand, such as, for example, R′₃N,R′₂N(CH₂)_(n)NR′₂, substituted or unsubstituted 2,2′-bipyridine or1,10-phenanthroline, a phosphite P(OR′)₃, an alkylphosphine P(alkyl)₃,an ether R′—O—R′, a diether, a thioether R′—S—R′ or a dithioether. R inturn can be alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, alkylaryl oralkynyl having at least one SiR′₃ or COOR′ group. R′ can be,independently of one another, R or H, alkyl, cycloalkyl, alkenyl,cycloalkenyl, aryl, alkylaryl or alkynyl.

Alkyl groups can be straight-chain or branched C1–C30-alkyl, preferablystraight-chain or branched C1–C9-alkyl, particularly preferablystraight-chain or branched C1–C4-alkyl from the group consisting ofmethyl, ethyl, n- and i-propyl and n-, i- and tert-butyl. Cycloalkylgroups can be straight-chain or branched C3–C30-cycloalkyl, preferablyC3–C9-cycloalkyl, particularly preferably C3–C6-cycloalkyl from thegroup consisting of cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.

Alkenyl groups can be straight-chain or branched C2–C30-alkenyl,preferably straight-chain or branched C2–C9-alkenyl, particularlypreferably straight-chain or branched C2–C6-alkenyl from the groupconsisting of vinyl, propenyl, butenyl, pentenyl and hexenyl.Cycloalkenyl groups can be straight-chain or branchedC3–C30-cycloalkenyl, preferably C3–C9-cycloalkenyl, particularlypreferably C3–C6-cycloalkenyl from the group consisting ofcyclopropenyl, cyclobutenyl, cyclopentenyl, cyclopentadienyl andmethylcyclopentadienyl.

Aryl groups can be C6–C10-aryl, preferably phenyl or naphthyl. Alkylarylcan be C7–C18-alkylaryl, preferably tolyl or mesityl.

Alkynyl groups can be straight-chain or branched C2–C30-alkynyl,preferably straight-chain or branched C2–C9-alkynyl, particularlypreferably straight-chain or branched C2–C6-alkynyl from the groupconsisting of ethynyl, propynyl, butynyl, pentynyl and hexynyl.

Particularly suitable neutral Lewis bases are alkynes of the formulaR—C≡C—R′ and alkenes of the formula R′HC═CHR which contain at least onesilyl or ester group. Preference is given to the use of alkynes from theR′₃Si—C≡C—R′ group, and particularly good results are obtained with thealkynes Me₃Si—C≡C—R′ (R′=SiMe₃, CH₃, C₂H₅, C₃H₇, C₄H₉, phenyl, COOMe,COOEt) and with the alkynes MeOOC—C≡C—COOMe and EtOOC—C≡C—COOEt.Preference is given to the use of alkenes from the R′HC═CHR group, andparticularly good properties are obtained with the alkenes H₂C═CHSiMe₃,H₂C═CHSiR′₃, in which R′, independently of one another, can be CH₃,C₂H₅, C₃H₇, C₄H₉, HC═CH₂ or phenyl, and with the alkenes H₂C═CHCOOCH₃and H₂C═CHCOOC₂H₅. Particularly good results are obtained with thealkynes Me₃Si—C≡C—SiMe₃, Me₃Si—C≡C—^(n)Bu and the alkenes H₂C═CHSiEt₂Me,H₂C═CHSiMe₂ ^(t)Bu.

The following are also suitable as neutral Lewis bases: nitriles R′C≡N,for example CH₃—C≡N, ^(t)Bu C≡N, C₄H₉C≡N or Ph—C≡N; saturated orunsaturated nitrogen ligands R′₃N, such as, for example, N(CH₃)₃,N(C₂H₅)₃ or R′₂N(CH₂)_(n)NR′₂, such as, for example, H₂N—(CH₂)₂—NH₂,(CH₃)₂N—(CH₂)₂—N(CH₃)₂, (C₂H₅)₂N—(CH₂)₂—N(C₂H₅)₂, H₂N—(CH₂)₄—NH₂,(CH₃)₂N—(CH₂)₄—N(CH₃)₂, (C₂H₅)₂N—(CH₂)₄—N(C₂H₅)₂ or substituted orunsubstituted 2,2′-bipyridine or 1,10-phenanthroline or2,9-dimethyl-1,10-phenanthroline; phosphites of the formula P(OR′)₃, forexample P(OCH₃)₃, P(OC₂H₅)₃, P(OC₆H₁₁)₃ or P(OPh)₃; trialkylphosphinesof the formula PR′₃, for example P(CH₃)₃, P(C₂H₅)₃, P(C₃H₇)₃, P(C₄H₉)₃or P(C₆H₁₁)₃; ethers of the formulae R′—O—R′ and R′O—(CR′₂)_(n)—OR′, forexample C₂H₅—O—C₂H₅, CH₃—O—C₄H₉, CH₃O—(CH₂)₂—OCH₃ or C₂H₅O—(CH₂)₂—OC₂H₅;thioethers of the formulae R′—S—R′ and R′S—(CR′₂)_(n)—SR′, for exampleCH₃—S—CH₃, C₂H₅—S—C₂H₅, C₃H₇—S—C₃H₇, Ph—S—Ph, Ch₃S—(CH₂)₂—SCH₃,CH₃S—(CH₂)₃—SCH₃, C₂H₅S—(CH₂)₂—SC₂H₅ or PhS—(CH₂)₂—SPh.

The compounds of the general formula (I) are prepared by reaction ofCu₂O, oxalic acid and the Lewis base L under a protective-gas atmospherein an inert aprotic organic solvent. The Lewis base L employed for thispurpose can be two different Lewis bases L in an equimolar ratio. Thesequence of addition of the components can be selected as desired. Ifthe Lewis base L to be employed is a mixture of two correspondingcompounds, the two compounds are preferably added to the reactionmixture simultaneously or mixed with one another before the addition.The starting compounds can be pre-dissolved or suspended in a suitablesolvent or added without solvent as a solid or liquid. Suitable solventswhich can be used for carrying out the reaction are inert aproticsolvents, such as open-chain or cyclic aliphatic and aromatichydrocarbons, which may be partially halogenated, or ethers and cyclicethers. Particular preference is given to the use of pentane, hexane,heptane, cyclohexane, toluene, methylene chloride, trichloro-methane,chlorobenzene, diethyl ether or tetrahydrofuran. The protective-gasatmosphere used can be nitrogen or argon. The stoichiometric ratio ofthe starting materials Cu₂O, oxalic acid and the Lewis base L is between1:1:2 and 1:1:4, preferably between 1:1:2 and 1:1:3 and particularlypreferably 1:1:2. The Lewis base L should not be added in asub-stoichiometric amount with respect to oxalic acid and Cu₂O. Thereaction can be carried out at a temperature in the range from −30 to+100° C., preferably from 0 to 50° C. and very preferably between 20 and40° C. The highest yields are obtained at room temperature. The reactiontime is between 1 and 24 hours, preferably between 2 and 8 hours andvery preferably between 3 and 6 hours. The reaction solution changesbeginning from a red suspension to a colourless or brownish solution orsuspension, depending on the type of complex formed. The insolubleconstituents are separated off. This can be carried out by filtration,centrifugation or other methods known to the person skilled in the art.A clear colourless, yellow or red solution is obtained, depending on thetype of Lewis base L employed. The compounds of the general formula (I)are subsequently isolated. This can be carried out after the removal ofthe solvent by methods known to the person skilled in the art. Ifnecessary, further purification is carried out. Instead of mechanicalseparation of the solids from the reaction mixture by filtration orother methods, it is also possible to carry out an extraction in orderto remove the product formed. The compounds of the general formula (I)are, as already described above, surprisingly temperature-stable and cantherefore be isolated well as pure substances and subsequentlycharacterised analytically and spectroscopically.

The thermal behaviour of the compounds can be investigated by means ofTGA (thermogravimetric analysis) and DSC (differential scanningcalorimetry). Investigations carried out have shown that thedecomposition of the compounds according to the invention takes place in2 main steps:

Firstly, the Lewis base L is eliminated from the copper(I) complex. Thiselimination can also take place stepwise, depending on the compound, andcan be detected by TGA. In the second step, decarboxylation takes placewith formation of metallic copper and carbon dioxide through an internalredox reaction of the remaining fragment CuO₂C₂O₂Cu. The first step iscarried out, depending on the precursor, at a temperature in the rangefrom about 50 to about 200° C., and the second from about 150° C. and iscomplete at about 350° C. However, it is entirely possible for theelimination of the Lewis bases and the decarboxylation reaction toproceed in parallel on transition to higher temperatures. The residualcontent corresponds precisely to the copper content in the correspondingcopper(I) precursor, so that the yield of metallic copper is 100% withthe compounds of the general formula (I) and is thus double that of theprior art.

This efficient decomposition reaction results in fewer by-products withthe compounds of the general formula (I) compared with the prior art.The free Lewis base L re-forms in the deposition process and can becollected by appropriate devices, such as, for example, cold traps inthe exhaust air, and re-used; the second by-product formed in carbondioxide. Compared with the prior art, in which copper(II)hexafluoroacetylacetonate and the Lewis base trimethylvinylsilane areformed as by-products, the by-products are copper-free, nontoxic andthus safer. The environmental pollution is thus significantly less thanon use of the compounds of the prior art.

(Me₃Si—C≡C—SiMe₃)₂Cu₂O₄C₂ has proven to be a thermally stable compoundwhich is extremely insensitive to oxidation. The compound is stable upto 100° C. and can be handled in air over a period of weeks. This is anenormous advance compared with the prior art since CupraSelect®decomposes slowly even from about 50° C. and the compound is alsorapidly oxidised in air to give copper(II). This enables very muchsimpler handling not only in the synthesis, but also in the depositionprocess.

The compounds of the general formula (I) can be used as precursors forthe deposition of metallic copper. The deposition of metallic copperfilms can take place from the gas phase or from a solution of precursorand a suitable solvent or from the solid state of the precursor throughcontact of the precursor with a heated substrate.

For illustration and for better understanding of the present invention,examples are given below. However, owing to the general validity of theinventive principle described, these are not suitable for reducing thescope of protection of the present application to just these examples.Furthermore, the contents of the cited patent applications are to beregarded as part of the disclosure content of the present inventionwhich forms the basis of the description.

4. EXAMPLES Example 1 Di{[bis(trimethylsilyl)acetylene]copper(I)}oxalate

8 g of Me₃SiC≡CSiMe₃ and 2.14 g of oxalic acid are added to a suspensionof 3.4 g of Cu₂O in 30 ml of methylene chloride under an inert-gasatmosphere, and the mixture is stirred at room temperature for 4 hours.In order to remove insoluble residues, the solution is passed through afrit with silica gel, and the residue is washed twice with methylenechloride on the frit. The colourless solution is evaporated, andcolourless crystals of (Me₃SiC≡CSiMe₃)₂Cu₂O₄C₂ are obtained at −30° C.

C₁₈H₃₆Cu₂O₄Si₄ (555.92 g/mol). Analysis [%]: calculated: C 38.9, H 6.5,found: C 38.7, H 6.6. IR (KBr) [cm⁻¹]: ν_(C≡C) 1935, ν_(CO2) 1642, 1354,1309. ¹H-NMR (CDCl₃) [ppm]: 0.30 (s, 36H, SiMe₃). ¹³C-NMR (CDCl₃) [ppm]:0.0 (SiMe₃), 114.2 (C≡C), 171.8 (CO₂). MS (m/e (%)): 788 (25)[M+Cu(Me₃SiC≡CSiMe₃)]⁺, 618 (10) [M+Cu]⁺, 403 (68) [M−CuO₄C₂]⁺,233 (100)[M−(Me₃SiC≡CSiMe₃)CuO₄C₂]⁺. TG (30–1000° C., 5° C./min) two-stepdecomposition, 1st step temperature range 100–170° C., weight drop 65%(2 Me₃SiC≡CSiMe₃), 2nd step temperature range 230–290° C., weight drop11% (2 CO₂), residual content 24% (2 Cu).

FIG. 1 shows the decomposition of thedi{[bis(trimethylsilyl)acetylene]-copper(I)}oxalate prepared as afunction of temperature with deposition of a thin copper layer on asubstrate.

Example 2 Di{[(trimethylsilyl)(n-butyl)acetylene]copper(I)}oxalate

5 ml of Me₃SiC≡C^(n)Bu and 1.13 g of oxalic acid are added to asuspension of 1.8 g of Cu₂O in 400 ml of methylene chloride under aninert-gas atmosphere, and the mixture is stirred at room temperature for5 hours. In order to remove insoluble residues, the solution is passedthrough a frit with silica gel, and the residue is washed twice withmethylene chloride on the frit. The colourless solution is evaporated,and colourless crystals of (Me₃SiC≡C^(n)Bu)₂Cu₂O₄C₂ are obtained at −30°C.

C₂₀H₃₆Cu₂O₄Si₂ (523.77 g/mol). IR (KBr) [cm⁻¹]: ν_(C≡C) 1986, ν_(CO2)1643, 1355, 1311. ¹H-NMR (CDCl₃) [ppm]: 0.29 (s, 18H, SiMe₃), 0.93 [t,³J_(HH)=7.0 Hz, 6H, (CH₂)₃CH₃], 1.3–1.6 [m, 4H, (CH₂)₂CH₂CH_(3],)1.5–1.8 (m, 4H, CH₂CH₂CH₂CH₃), 2.58 [t, ³J_(HH)=7.0 Hz, 4H,CH₂(CH₂)₂Ch₃]. ¹³C—(CDCl₃) [ppm]: 0.0 (SiMe₃), 13.4 [(CH₂)₃CH₃], 21.7[(CH₂)₂CH₂CH₃], 22.5 (CH₂CH₂CH₂CH₃), 30.9 (≡CCH₂), 85.4 (≡CCH₂), 112.9(SiC≡C), 171.4 (CO₂). MS (m/e (%)): 741 (20) [M+Cu(Me₃SiC≡CBu)]⁺, 587(20) [M+Cu]⁺, 371 (93) [M−CuO₄C₂]⁺, 217 (100) [M−(Me₃SiC≡CBu)CuO₄C₂]⁺.TG (30–1000° C., 5° C./min) two-step decomposition, 1st step temperaturerange 70–150° C., weight drop 53% (2 Me₃SiC≡CBu), 2nd step temperaturerange 170–300° C., weight drop 23% (2 CO₂), residual content 24% (2 Cu).

FIG. 2 shows the decomposition of thedi{[(trimethylsilyl)(n-butyl)-acetylene]copper(I)}oxalate prepared as afunction of temperature with deposition of a thin copper layer on asubstrate.

Example 3 Di[(vinyl-t-butyldimethylsilane)copper(I)]oxalate

4.8 ml of H₂C═CHSiMe₂ ^(t)Bu and 1.13 g of oxalic acid are added to asuspension of 1.8 g of Cu₂O in 400 ml of methylene chloride under aninert-gas atmosphere, and the mixture is stirred at room temperature for5 hours. In order to remove insoluble residues, the solution is passedthrough a frit with silica gel, and the residue is washed twice withmethylene chloride on the frit. The colourless solution is evaporated,and colourless crystals of (H₂C═CHSiMe₂ ^(t)Bu)₂Cu₂O₄C₂ are obtained at−30° C.

C₁₈H₃₆Cu₂O₄Si₂ (499.75 g/mol). IR (KBr) [cm⁻¹]: ν_(CO2) 1647, 1344,1312. ¹H-NMR (CDCl₃) [ppm]: 0.14 (s, 12H, Si(CH₃)₂), 0.90 (s, 18H,C(CH₃)₃), 4.50 (dd, J_(trans)=18.3 Hz, J_(gem)=2.5 Hz, 2H, SiCH═CH₂),4.78 (dd, J_(trans)=18.3 Hz, J_(cis)=13.3 Hz, 2H, SiCH═CH₂), 4.86 (dd,J_(cis)=13.3 Hz, J_(gem)=2.5 Hz, 2H, SiCH═CH₂). ¹³C-NMR (CDCl₃) [ppm]:−5.8 (SiMe₂), 16.8 (CMe₃), 26.2 (CMe₃), 91.0 (═CH₂), 97.4 (═CHSi), 171.6(CO₂). MS (m/e (%)): 347 (62) [M−CUO₄C₂]⁺, 206 (80)[M−(H₂C═CHSiMe₂Bu)CUO₄C₂]⁺. TG (30-1000° C., 5° C./min) three-stepdecomposition, 1st step temperature range 70–130° C., weight drop 39%(H₂C═CHSiMe₂ ^(t)Bu, H₂C═CMe₂), 2nd step temperature range 130–170° C.,weight drop 15% (H₂C═CHSiMe₂H), 3rd step temperature range 170–310° C.,weight drop 19% (2 CO₂), residual content 27% (2 Cu).

FIG. 3 shows the decomposition of thedi[(vinyl-t-butyldimethylsilane)-copper(I)]oxalate prepared as afunction of temperature with deposition of a thin copper layer on asubstrate.

Example 4 Di[(vinyldiethylmethylsilane)copper(I)]oxalate

4.4 ml of H₂C═CHSiEt₂Me and 1.1 g of oxalic acid are added to asuspension of 1.8 g of Cu₂O in 400 ml of methylene chloride under aninert-gas atmosphere, and the mixture is stirred at room temperature for5 hours. In order to remove insoluble residues, the solution is passedthrough a frit with silica gel, and the residue is washed twice withmethylene chloride on the frit. The colourless solution is evaporated,and colourless crystals of (H₂C═CHSiEt₂Me)₂Cu₂O₄C₂ are obtained at −30°C.

C₁₆H₃₂Cu₂O₄Si₂ (471.70 g/mol). IR (KBr) [cm⁻¹]: ν_(C═C) 1496; ν_(CO2)1645, 1343, 1310. ¹H-NMR (CDCl₃) [ppm]: 0.12 (s, 6H, SiMe), 0.65 (q, 8H,³J=7.8 Hz, CH₂), 0.98 (t, 12H, ³J=7.9 Hz, CH₃), 4.48 (dd, J_(trans)=17.5Hz, J_(gem)=3.6 Hz, 2H, SiCH═CHH), 4.75 (dd, J_(trans)=17.7 Hz,J_(cis)=13.0 Hz, 2H, SiCH═CH₂), 4.81 (dd, J_(cis)=13.0 Hz, J_(gem)=3.5Hz, 2H, SiCH═CHH). ¹³C-NMR (CDCl₃) [ppm]: −5.5 (SiCH₃), 5.3 (SiCH₂CH₃),7.3 (SiCH₂CH₃), 89.7 (H₂C═CH), 96.6 (H₂C═CH), 171.5 (COO). TG (30–1000°C., 5° C./min) two-step decomposition, 1st step temperature range50–150° C., weight drop 50% (2H₂C═CHSiEt₂Me), 2nd step temperature range150–320° C., weight drop 23% (2 CO₂), residual content 27% (2 Cu).

FIG. 4 shows the decomposition of thedi[(vinyldiethylmethylsilane)-copper(I)]oxalate prepared as a functionof temperature with deposition of a thin copper layer on a substrate.

1. A Compound of formula (I)

in which copper is in the oxidation state +1, and L is R—C≡C—R′ havingat least one silyl or ester group, R′HC═CHR having at least one silyl orester group, R′₃Si—C≡C—R′, R′₃N, R′₂N(CH₂)_(n)NR′₂, substituted orunsubstituted 2,2′-bipyridine, 1,10-phenanthroline, P(OR′)₃, P(alkyl)₃,R′—O—R′, R′—O(CH₂)_(n)O—R′, R′—S—R′, R′—S(CH₂)_(n)S—R′, CH₃—C≡N,^(t)Bu—C≡N, C₄H₉C≡N or Ph—C≡N, where R is A, aryl, alkylaryl or alkynylhaving at least one SiR′₃ or COOR′ group, and R′ is R, H, A, aryl,alkylaryl or alkynyl, where L, R and R′ may each, independently of oneanother, adopt identical or different meanings in different positions ofthe molecule, and A is straight-chain or branched C1–C30-alkyl,C3–C30-cycloalkyl, straight-chain or branched C2–C30-alkenyl orstraight-chain or branched C3–C30-cycloalkenyl, aryl is C6–C10-aryl oralkylaryl, alkylaryl is C7–C18-alkylaryl, alkynyl is straight-chain orbranched C2–C30-alkynyl.
 2. A compound according to claim 1, in which Ais straight-chain or branched C1–C9-alkyl, straight-chain or branchedC3–C9-cycloalkyl, straight-chain or branched C2–C9-alkenyl orstraight-chain or branched C3–C9-cycloalkenyl, aryl is phenyl ornaphthyl, alkylaryl is tolyl or mesityl, alkynyl is straight-chain orbranched C2–C9-alkynyl, and R and R′ may each, independently of oneanother, adopt identical or different meanings in different positions ofthe molecule.
 3. A compound according to claim 1, in which A is methyl,ethyl, n- and i-propyl and n-, i-tert-butyl, cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, vinyl, C2–C6- alkenyl, propenyl, butenyl,pentenyl, hexenyl, cyclopropenyl, cyclobutenyl, cyclopentenyl,cyclopentadienyl or methylcyclopentadienyl, aryl is phenyl or naphthyl,alkylaryl is tolyl or mesityl, alkynyl is ethynyl, propynyl, butynyl,pentynyl or hexynyl, and R and R′ may each, independently of oneanother, adopt identical or different meanings in different positions ofthe molecule.
 4. A compound according to claim 1, in which L is R—C≡C—R′or R′HC═CHR, each having at least one silyl or ester group, and theradicals R and R′ are as defined in claim
 1. 5. A compound according toclaim 1, in which L is R′₃Si—C≡C—R′, where R′ is SiMe₃, CH₃, C₂H₅, C₃H₇,C₄H₉, phenyl, COOMe or COOEt.
 6. A compound according to claim 1, inwhich L is Me₃SiC≡C—SiMe₃, Me₃Si—C≡C—^(n)Bu, McOOC—C≡C—COOMe,EtOOC—C≡C—COOEt or Me₃Si—C≡C—R′, in which R′ is CH₃, C₂H₅, C₃H₇, phenyl,COOMe or COOEt.
 7. A compound according to claim 1, in which L isH₂C═CHSiMe₃, H₂C═CHCOOCH₃, H₂C═CHCOOC₂H₅ or H₂C═CHSiR′₃, in which R′,independently of one another, is CH₃, C₂H₅, C₃H₇, C₄H₉, HC═CH₂ orphenyl.
 8. A compound according to claim 1, in which L is CH₃—C≡N,^(t)Bu C≡N, C₄H₉C≡N, Ph—C≡N; N(CH₃)₃, N(C₂H₅)₃, H₂N (CH₂)₂ ⁻NH₂,(CH₃)₂N⁻(CH₂)₂—N(CH₃)₂, (C₂H₅) ₂N⁻(CH₂)₂ ⁻N(C₂H₅)₂, H₂N—(CH₂)₄—NH₂,(CH₃)₂N—(CH₂)₄—N(CH₃)₂, (C₂H₅)₂N⁻(CH₂)₄N(C₂H₅)₂,2,9-dimethyl-1,10-phenanthroline; P(OCH₃)₃, P(OC₂H₅)₃, P(OC₆H₁₁)₃,P(OPh)₃; P(CH₃)₃, P(C₂H₅)₃, P(C₃H₇)₃, P(C₄H₉)₃, P(C₆H₁₁)₃; C₂H₅—O—C₂H₅,CH₃—O—C₄H₉, CH₃O—(CH₂)₂—OCH₃, C₂H₅O—(CH₂)₂—OC₂H₅, CH₃—S—CH₃,C₂H₅—S—C₂H₅, C₃H₇—S—C₃H₇, Ph—S—Ph, Ch₃S—(CH₂)₂—SCH₃, CH₃S—(CH₂)₃—SCH₃,C₂H₅S—(CH₂)₂—SC₂H₅ or PhS—(CH₂)₂—SPh.
 9. A compounds of formula (I)di{[bis(trimethylsilyl)acetylene]copper(I)}oxalate,di{[(trimethylsilyl)(n-butyl)acetylene]copper(I)}oxalate,di[(vinyl-t-butyldimethylsilane)copper(I)]oxalate,di[(vinyldiethylmethylsilane)copper(I)]oxalate.
 10. A process for thepreparation of a compound of the general formula (I) according to claim1, comprising reacting Cu₂O with oxalic acid and a Lewis base L in aninert solvent, and isolating the resultant product.
 11. A processaccording to claim 10, wherein an inert aprotic organic solvent is usedwhich is an open-chain or cyclic aliphatic or aromatic hydrocarbon, ahalogenated aliphatic or halogenated aromatic hydrocarbon or a linear orcyclic ether or a mixture of these hydrocarbons.
 12. A process accordingto claim 10, further comprising utilizing a solvent which is pentane,hexane, heptane, cyclohexane, toluene, methylene chloride,trichloromethane, chlorobenzene, diethyl ether or tetrahydrofuran.
 13. Aprocess according to claim 10, carried out under a protective-gasatmosphere.
 14. A process according to claim 13, wherein the protectivegas employed is nitrogen or argon.
 15. A process according to claim 10,wherein the Lewis base L is employed in at least twice thestoichiometric ratio of the starting materials Cu₂O and oxalic acid. 16.A process according to claim 10, wherein the starting materials Cu₂O,oxalic acid and Lewis base L are employed in a stoichiometric ratio offrom 1:1:2 to 1:1:4.
 17. A process according to claim 10, wherein twodifferent Lewis bases L are employed in identical molar amounts.
 18. Aprocess according to claim 10, wherein the reaction is carried outwithin a reaction time of from about 1 to 24 hours at a temperature inthe range from about −30 to +100° C.
 19. A process according to claim10, carried out at room temperature.
 20. A process according to claim10, wherein, when the reaction is complete, insoluble constituents areseparated off, and the reaction product is isolated from the solutionand, if necessary, purified, or in that the reaction product isseparated from the reaction mixture by extraction, isolated and, ifnecessary, purified.
 21. A process according to claim 10, whereininsoluble constituents are separated off by filtration.
 22. A processfor the production of highly pure, thin metallic copper layers, whereincompounds of metallic copper layers, wherein compounds of formula (I)according to claim 1 are heated, causing elimination of the Lewis base Land deposition of metallic copper deposited through decarboxylation. 23.A process according to claim 22, wherein the elimination of the Lewisbase L is carried out at a temperature in the range from about 50 toabout 200° C., and the decarboxylation is completed at a temperature inthe range from about 150 to 350° C. with formation of metallic copper.24. A process according to claim 22, wherein the Lewis base L eliminatedis recycled and, re-employed in a process for preparing compounds ofgeneral formula (I) by reacting Cu₂O with oxalic acid and the Lewis basein an inert solvent and isolating the product, and then the resultantcompounds of formula (I) are used for the production of highly pure,thin metallic copper layers.